Motorcycle Repair: motor year?, honda shop, head gasket

Question
I have a 1976 honda been fixing up the guy I got it from did not think the motor was the same he thinks it is a 73 the No# on motor is CB750-2537235 How do or can find out year of motor Needs Head gasket to get rolling.
Thanks for any help
Gary

Answer
Gary, I don't know of any way to cross reference the engine serial number to a model year.  When you go to buy parts, the parts are referenced to the frame serial number.  The good news is that most of those engines were the same.  The later headgaskets were a little different as Honda tried to find a design that didn't leak at the corners.  Once you get the head off you'll have to go to the Honda shop and see if you can match up the configuration you have to the parts catalog.  The main difference was the O-rings around the oil passages around the studs.  Later models had O-rings and dowels around all of the front studs while earlier models just had them in the corner studs.

Regards
Rich